Gun firing mechanism



Jan. 30, 1968 R. J. CASULL GUN FIRING MECHANISM 4 Sheets-$heet 1 Original Filed Aug. 27, 1964 @Q ,U T

A UHIW INVENTQR ATTORNEY Jan. 30, 1968' J. CASULL 3,366,010

GUN FIRING MECHANISM 4 Sheets-Sheet Driginal Filed Aug. 27, 1964 FIG. 3.

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INVENTOR RICHARD J. CASULL BY KM/ A'1'"TORNEY Jan. 30, 1968 R. J. CASULL GUN FIRING MECHANISM Original Filed Aug. 27, 1964 4 Sheets-Sheet 3 FIG. 3A.

FIG. 3B.

a Gb 5 6 i 1 FIG. 6. I 86 INVENTOR RICHARD J. CASULL BY am, a

ATTORNEY Jan. 30, 1968 R. .1. CAS ULL GUN FIRING MECHANISM 4-Sheets-Sheet 4 Original Filed Aug. 27, 1964 FIG. 9.

FIG. 8.

FIG. 11.

FIG. 10.

FIG. 13.

FIG. 12.

INVENTOR RICHARD J. CASULL TTORNEY United States Patent 1 Claim. (Cl. 89-140) ABSTRACT OF THE DISELOSURE A firing mechanism for a gun including a pivotally mounted sear lock engageable at one end by a sliding bolt and axially movable thereby against the force of spring means within the lock to place the opposite end of the lock in proximity to a pivotal trigger.

This invention relates generally to guns of the rapid firing type and more particularly to a selector mechanism for sub-machine guns.

This application is a division of my copending application Ser. No. 392,540, filed Aug. 27, 1964, now Patent No. 3,319,523.

Many of the present machine guns lack several of the advantages sought in this type of device. In view of the environment wherein machine guns will be found, namely, the military and law enforcement agencies, due to the laws attendant to their possession, it is of primary importance that the user be able to quickly attach a magazine containing the maximum number of rounds of cartridges to the weapon. To further facilitate the use of the device it is also most advantageous to have ready means for changing the barrel and for adjusting the h-ead-space, thereof while in the field where specialized tools are unavailable.

Accordingly, one of the objects of the present invention is to provide a sub-machine gun having a rapidly attachable drum-type magazine mounted above the top of the receiver and containing an exceptionally large number of rounds in the small space involved.

Another object of the invention is to provide a machine gun having a drum-type cartridge magazine having novel feeding means to insure dependability in the feeding and ejection of the cartridges regardless of the position in which the weapon is held.

A still further object of the invention is to provide a machine gun operated by the recoil or blow-back principle and including a pivotal guide arm which is oscillated by the movement of the bolt to assist in the feeding and ejecting of the cartridges.

Another object of the invention is to provide a machine gun having a quickly detachable barrel which may be removed without the use of special tools.

A still further object of the invention is to provide a sub-machine gun having novel means for changing its operation from semi-automatic to full automatic firing.

With these and other objects in view, which will more readily appear as the nature of the invention is better understood, the invention consists in the novel construction, combination and arrangement of parts hereinafter more fully described, illustrated and claimed.

FIGURE 1 is a vertical sectional view of a machine gun according to the invention.

FIGURE la is a top plan view of the top catch plate forming part of the cartridge drum feeding mechanism.

FIGURE 2 is a partial top horizontal sectional view of the machine gun as seen in FIGURE 1.

is provided in the FIGURE 3 is a partial vertical sectional view showing the bolt, trigger mechanism, and bolt sear lock in the closed position, with the selector in the semi-automatic position.

FIGURE 3a is a partial vertical sectional view of the mechanism as in FIGURE 3 but with the bolt in the cocked or ready position.

FIGURE 3b is a partial vertical sectional view of the device shown in FIGURE 3 but with the trigger depressed and the weapon having been fired.

FIGURE 4 is a partial vertical sectional view of the trigger mechanism and bolt sear lock similar to FIGURE 3 but with the selector in the full-automatic position.

FIGURE 5 is a partial horizontal sectional view illustrating the selector passing through the trigger assembly shown in FIGURES 3 and 4.

FIGURE 6 is a partial bottom plan view of the bullet guide plate and guide arm.

FIGURE 6a is a top plan view of the bullet guide plate.

FIGURE 7 is a side elevation, partly in section, of the bullet guide arm and guide plate.

FIGURE 8 is a top plan view of the drum housing.

FIGURE 9 is a top plan view of the bullet separator.

FIGURE 10 is a partial vertical section through the drum housing.

FIGURE 11 is a side elevation of the bullet separator.

FIGURE 12 is a top plan view, partly broken away, and partially illustrates the drum and separator assembly as it applies to the vertical bullet separation.

FIGURE 13 is a vertical section of the assembly of FIGURE 12.

Similar reference characters designate corresponding parts throughout the several figures of the drawings.

Referring now to the drawings, particularly FIGURE 1, it will be seen that the sub-machine gun comprises a barrel 1 slidably fitted against the forward portion of a receiver 2 and retained thereagainst by means of a barrel locking mechanism generally designated 3, and mounted in the forward portion of the receiver 2. The rearmost portion of the barrel contains a notch 4 for engaging a mating projection 5 on the rear of a barrel lock 6. Spring 7 constantly urges the forward portion 8 of the barrel lock 6 downwardly so that the lock 6 pivots about the pin 9 to urge the projection 5 upward into the notch 4.

Referring now also to FIGURE 2, it will be noted that the pin 9 is disposed within an elongated slot 9a formed through the forward portion of the receiver 2. The forwardmost edge of the receiver is provided with a pair of machine screws 10 which may be adjustably positioned to vary the position of the pin 9 and therefore the lock 6 with respect to the receiver 2. Thus it will be seen that by manipulating the position of the screws 10 the longitudinal adjustment of the projection 5 of the lock 6 may be altered to selectively determine the relative position of the barrel 1 which engages the projection 5 by means of the notch 4. Suitable heavy coil springs 6b, 6b are seated in the receiver on the one end, and bear against the pin 9 on the other, to maintain the pin in constant engagement with the ends of the screws 10.

The preceding arrangement provides quick and accurate adjustment of the weapons headspace, or distance between the rear face of the barrel and the forward face of the bolt when in its locked position.

Disposed within the rearward portion of the receiver 2 is a bolt 11. This bolt is of the solid type, that is, it is provided with an integral rigid firing pin 12 on its forward nose portion 13. Removably mounted on one side of the bolt 11 is a cocking handle 14 retained in the side of the bolt by means of pin 15. A longitudinally opening 16 side of the receiver to accommodate the reciprocating movement of said cocking handle. A

longitudinal bore 17 opening to the rear of the bolt receives the mainspring 18. The rear of the mainspring 18 is supported and guided by means of mainspring guide 19 attached to the rear wall 20 of the receiver. Pivotally mounted upon the side of the receiver opposite that of the cocking handle 14 is an oscillating bullet guide arm 21 adapted to pivot about the pin 22. The rear portion of the bullet guide arm 21 is enlarged to provide a rear projection 21a, while the forward portion is enlarged to form a reciprocating bullet guide 23.The side of the bolt immediately adjacent the oscillating bullet guide arm 21 is provided with a cam surface 24 which, as will be seen by viewing FIGURE 2, abuts the rear projection 21a on the guide arm 21 when the bolt is in its rearmost or retracted position. Similarly, when the bolt travels to its forward or closed position as viewed in FIGURE 2, the forward nose portion 13 of the bolt strikes the guide arm 21 and causes return of the bullet guide arm 21 to the position shown in this figure. The function of this bullet guide arm will be described hereinafter.

' Mounted on top of the receiver is a sliding drum lock receiver sight base 25. Longitudinal movement is imparted to the drum lock by means of locking cam 26 pivotally mounted to the top of the receiver as at 27. As the sliding drum lock cam 26 is pivotally rotated by means of manual pressure upon the finger tab 27a it will be seen that the drum lock 25 will be retracted or removed to the right as viewed in FIGURE 1. The forward lower side edges of the drum lock are provided with locking recesses 28 which engage the rear peripheral edges 29 of the base plate of the drum assembly D. As the drum lock 25 is retracted the recess 28 is moved from engagement with the drum assembly 29. The above action is the only step necessary in order to unlock the drum assembly 29 so that the empty drum housing D may be removed and replaced with a loaded drum of cartridges.

Mounted beneath the receiver 2 is the trigger housing 30 which may in turn form a mounting base for receiving any suitable type of stock member such as the pistol grip stock 31 shown in the drawings. FIGURES 3-5 may be referred to in connection with the specific arrangement of the. trigger and sear construction.

' As noted, the trigger, generally designated 32, comprises two primary sections, namely, the main trigger section 33 which is provided with a longitudinal U-shaped channel 34 for receiving the slidable disconnector 35. A transverse opening 36 is provided through both side walls of the main trigger section, as well as the medially disposed disconnector section 35 for slidably receiving the selector 38. A spring 39'mounted in a bore in the forward portion of the disconnector urges a plunger 40 against the selector to assist in maintaining the selector in one or the other of its two positions as will be described hereinafter. A somewhat similar spring-urged plunger 41 is mounted in the lower portion of the trigger housing 30 and constantly bears against the rear surface of the trigger 32 to urge the trigger to its forward, or at rest position, as shown in FIGURES 3 and 4.

'The portions of the selector extending from the two sides of the triggerare journaled in the adjacent side walls of the trigger housing 30 whereby pivotal support is provided the trigger. The openings in the side walls of the trigger housing 30 through which the ends of the selector pass are of circular cross section, as are the openings in the two side walls'42 of the trigger assembly. The selector 38'is generally of similar circular section and is mounted through said openings to provide a close fit which allows sliding movement to be imparted to the selector as well as pivotal movement of the trigger assembly around the selector.

An enclosed recess 43 formed in the medial portion of the selector 38 is adapted to cooperate with a mating chamfered edge 44 on the rear side of the transverse opening 36 in the disconnector 35 as will be most closely seen from FIGURE 5.

A bolt sear lock 45 mounted in a recess in the bottom of the receiver 2 includes an inclined recess 46 in its upper surface the effect of which is to provide a raised or locking surface 47 at the rear of the sear lock 45. An elongated transverse bore 48 is provided through the medial portion of the sear lock for receiving a pin 49 carried in the sides of the receiver 2. Suitable spring plunger means 50 is disposed inside the bolt sear lock for urging the sear lock to the position shown in FIG- URES 3 and 4, wherein it will be noted that the sear lock is normally urged to the far right with the pin 49 abutting the left-hand portion of the elongated bore 48. Mounted in the trigger housing immediately beneath the sear lock is a spring plunger 51 for applying a constant upward pressure against the undersurface of the sear lock. The contact surface of the plunger 51 is preferably rounded for reasons which will become apparent hereinafter.

As FIGURE 3a discloses the weapon in a cocked or ready-to-fire position, it will be understood that the bolt 11 has been drawn back against the force of rnainspring 18 and is retained in the open position by means of the locking surface 47 at the rear of the sear lock 45, which surface is constantly urged upwardly by spring plunger 51. The bolt is retained in its open position by the locking surface 47 which engages the bolt stop 52, comprising a notch in the opposed surface of the bolt. With the sear lock 45 engaging the bolt stop 52, it will be seen that the forward thrust of the mainspring 18 is transmitted through the sear lock and urges the sear forward against the force of the small spring plunger 50, an amount equal to the width of the elongated bore 48 in the sear.

The purpose and operation of the above structure will now be described. With the disconnector 35 urged towards the forward or semi-automatic position by the plunger 40 as shown in FIGURE 3a, it will be seen that when the trigger is depressed and thus pivots about the selector pin 38 the top rear corner 53 of the disconnector will pivot upwardly to strike the forward position 54 of the sear lock '45. This force pivots the sear lock around pin 49 to cause disengagement of the locking surface 47 from bolt stop 52 and subsequent forward movement of the bolt to effect firing. With the trigger released, the mechanism would appear as in FIGURE 3 at the moment of firing.

If the trigger is not then released and the disconnector 35 was set as shown in FIGURES 3 and 3a, then the trigger and sear lock would appear as in FIGURE 3b immediately after firing. In this position the lower forward edge 54 of the sear lock, which first drops downwardly when the locking surface 47 swings up into the bolt stop 52, and then moves partially forward as the spring plunger 50 yields to the mainspring pressure, strikes the back wall 53 of the disconnector 35. It will thus be seen that the weapon cannot be fired until the trigger is first released, whereupon the sear lock Will be moved forward the remainder of its travel within the limits of the bore 48, and will then appear as in FIGURE 3a.

FIGURES 4 and 5 illustrate the selector 38 positioned to provide for full automatic fire. The selector is moved to the right whereby the rear chamfered edge 44 of the transverse opening in the disconnector 35 is forced out of the inclined recess 43 in the selector. The disconnector is thus displaced rearwardly against the force of the spring plunger 40 so that the rear edge 53 thereof projects beyond the rear of the side walls 42 of the trigger assembly. With this setting, the rear edge 53 of the disconnector 35 is always disposed beneath and to the rear of the forward edge 54 of the sear lock whether the sear is in its forward or rear position so that when the trigger is pulled, the sear lock is held in a continuous disengaged position. For as long as the trigger is released, the bolt and sear lock assume the cocked or open position since the forward edge 54 of the sear lock is free to pivot downwardly against the force of spring plunger 51.

The cartridge drum assembly, generally designated D, is removably mounted upon the drum center post 55 secured to the barrel. The drum assembly includes a fiat substantially circular base plate 56 to which is attached a horizontal bullet separator 57 comprising a plurality of flat circular decks 58 interconnected to one another by means of inclined ramps 59 so that one continuous spirallike path is provided from the top of the free end 60 of the horizontal separator to the lower end 61 fixed to the base plate 56.

The drum post 55 may be attached to the top of the barrel by any suitable means insuring its rigid attachment thereto. The bottom of the post may, for example, be provided with a T-shaped base 55a, which mates with a correspondingly shaped transverse recess on the upper surface of the barrel.

A flat mounting surface 62 is formed on the top of the barrel and extends rearwardly on the top of the receiver to the forward portion of the sliding drum lock 25. The forward edge of the base plate 56 includes a tongue portion 63 having a medial indentation 64 adapted to engage a corresponding projection (not shown) disposed within an undercut recess 65 forming the forward limit of the mounting surface 62. The peripheral edge 29 of the base plate 56, diametrically opposed to the tongue 63, projects rearwardly to provide a forked locking flange cooperating with the aforementioned locking recesses 28 on the sliding drum lock 25.

A bushing collar 66 is centrally mounted over an opening in the base plate 56 and assists in initially orienting the drum assembly D during loading. The inside diameter of the collar 66 is somewhat larger than the diameter of the post 55 to permit the drum assembly to be sufficiently tilted during loading to allow the tongue 63 to engage the forward recess 65. The lack of a close fit between the collar 66 and post 55 does not preclude orientation of the drum assembly during loading since this is assured by the indentation 64 in the tongue 63 and the locking flange 29 at the rear of the plate 56 when the drum lock 25 is in its forwardmost position.

An opening 67 in the plate 56 is provided for admitting the cartridges C from the drum assembly to the inside of the receiver adjacent the chamber 68. This opening 67 is disposed intermediate the locking edges of flange 29 and adjacent the end 61 of the lowermost deck 58. The dimensions of the opening, which is disposed beneath the ramps 59, are such as to permit ready passage of a cartridge C therethrough without any binding contact.

Adapted to fit over the top of the horizontal bullet separator 57 is the circular drum housing, generally designated 69, and comprising a top wall 79 having depending inner and outer walls, 71 and 72 respectively. Spanning the circular opening between the base of the inner Wall 71 is a driving plate 73 having a central aperture adapted to slidably fit around the collar 66 of the base plate 56. Any suitable means such as the spring snap-ring 66a may be utilized to retain the drum housing 69 in position over the horizontal bullet separator 57.

The radial distance between the concentric inner and outer walls 71 and 72 is substantially greater than the width of the circular decks 58 of the horizontal bullet separator 57 for reasons which will immediately become apparent.

Adjacent decks 58 of the separator assembly 57 are vertically spaced from one another a distance which is slightly greater than the diameter of the casing of cartridges C to preclude binding during feeding.

The outer wall 72 includes a plurality of vertically disposed ribs 74 radially projecting from the inner side of the wall to a point just short of the outer edge of the decks 58. The ribs 74 are spaced from each other a distance slightly greater than the diameter of the cartridge rims C to provide a cavity 75 for the reception of the cartridge bases. The inner surface of the inner wall 71 is provided with a plurality of vertical grooves 76 having the ap proximate contour of the nose of the bullets C Since the grooves 76 are radially aligned with the cavities 75 it will be seen that positive means are provided by the drum housing 69 for insuring vertical alignment and separation of the cartridges C while the equispaced decks 58 of the separator 57 provide for horizontal separation and alignment.

With the foregoing structure in mind, it will be readily understood that a positive cartridge feeding arrangement is provided, wherein, clockwise rotary movement of the drum housing 69 imparts horizontal or rotary advancement of all the cartridges C. When the cartridges have been advanced by the ribs 74 and grooves 76 to the ramp portions 59, they fall by gravity as well as positive pressure down to the next lower deck. Additional guidance is offered by the ramp 53 next above the cartridges as they reach the end of each deck and are directed downwardly to the next lower deck, or through the opening 67 in the case of those cartridges on the lowermost deck. Each cartridge remains captive between a pair of opposed notches 76 and cavities 75 during its entire travel from an upper deck 58 until discharged through the opening 67.

The aforementioned driving plate 73, attached to the botttom of the inner wall 71 of the drum housing is provided with a plurality of upturned rachet teeth 77 which may be formed by upwardly striking portions of the plate '73 to present inclined elements having abutment edges 78 raised from the plate itself.

Driving means are provided in the form of a spring housing assembly 79 (FIGURES 1 and la) for rotating the drum housing 69 to feed the cartridges. This spring assembly includes a top catch plate 86* to which is attached a helically coiled clock-type driving spring 81 adapted to be lowered over the post 55 after the loaded drum housing 69 with the bullet separator 57 has been placed in position over the post.

A floating mounting sleeve 80a depends from the catch plate 86 and slidably fits over the center post 55. Suitable means are provided at the lower end of the sleeve 300, such as notches 8% which interlock with mating projections at the base of the post 55 for preventing rotary movement of the sleeve when in the position as shown in FIGURE 1.

The outermost convolution of the spring 81 is attached, as by welding, to a circular spring housing 81a surrounding the spring. The innermost end of the spring, on the other hand, is secured to the mounting sleeve 86a. The bottom edge of the housing 81a is provided with a plurality of projecting fingers 82 which extend downwardly to a point at least beneath the edges 78 of the teeth 77. With this arrangement, it is impossible for the spring 81 to unwind in a clockwise direction without turning of the drum housing and the resultant feeding of the cartridges, since the fingers 82 will strike the raised rachet teeth '77 to cause rotation of the plates 73 forming part of the drum housing.

To facilitate the winding of the spring, fingergrip openings may be provided in the catch plate 80 whereby the spring assembly may be manually rotated counter-clockwise against the force of the anchored spring 81. During such winding motion, the fingers 82 ride over and depress the ratchet teeth 77. Due to the inherent resiliency of the base plate material 73 from which the teeth are formed, these teeth immediately spring back up after the fingers 82 pass over the edges 78, which edges it will be seen prevent clockwise rotation of the spring assembly 79 without the drum hosuing 69. Alternatively, the teeth 77 can be rigidly disposed with respect to the plate 73 and the fingers 82 would therefore be vertically movable and spring urged downwardly (not shown).

To retain the complete cartridge feeding mechanism in position upon the machine gun, the diameter of the top plate 80 is formed sufiiciently large enough to overlie at least a portion of the top wall 79 of the drum housing 69. Positive means for locking the assembly in place are provided on the undersurface of the top plate 80 in the form of a pair of sliding catches 84 (FIGURE la.) each of which has a finger engaging portion 34a disposed beneath one of the finger openings in the catch plate and a locking edge 84b adapted to be slidably moved into and out a horizontal recess 55b in the center post 55. Suitable spring means such as leaf springs 89b, 8%, are anchored at one end of their ends to the undersurface of the top catch plate and have their other ends engaged by the catches to normally bias the catches outwardly to maintain the locking edges 84]) within the recesses 55!). As noted in FIGURE in, appropriate supporting blocks 80c, 80c retain the catches in mutual sliding abutment.

.. Withan understanding oftheflabove cartridge feeding structure in mind, it will be seen that after the spring assembly 79 has been wound up, the drum housing will be under constant tension and will be urging all of the cartridges C to move in a clockwise direction so that as long as there is at least one cartridge within the separator assembly 57, there will be a cartridge being urged through the opening 67 in the base plate 56.

' Since the force of the spring 81 is constant and there are no means included within the drum assembly for stopping and starting the discharge of cartridges from the opening 67, appropriate means are provided elsewhere for regulating the feeding of the cartridges from the drum assembly into the chamber 68, and the subsequent ejection of the spent casings from the weapon.

Fitted upon the top of the receiver 2, immediately beneath the opening 67 in the base plate, is a U-shaped bullet entrance guide plate 85 disposed with its top surface flush with the mounting surface 62 and having a longitudinal feed slot 86 below theopening 67.

As seen in FIGURES 2, 6, and 7, the bullet guide 23 on the forward part of the oscillating arm 21 is disposed beneath the guide slot 86 when the bolt is in the cocked, or ready-to-fire position. By this arrangement, the lowermost cartridge C being directed downwardly from the drum housing assembly will be supported upon the top surface of the guide 23 in a plane beneath the top surface of the guide plate 85 but slightly above the center axis of the barrel. When the sear is actuated to release the bolt, the upper section of the face of the bolt 11 strikes the rear of the cartridge to cause the bullet to contact the rounded forward web 85a of the guide plate 85 preparatory to entering the chamber v68. As the bolt continues its forward movement, the guide 23 will be forced outwardly away from its position beneath the slot 86 thereby permitting the cartridge to be axially aligned with the chamber as it is driven forward into firing position. During the period when the guide is pushed out of its bullet holding position the upper surface of the bolt supports the cartridges being urged downwardly from the drum assembly. It will be understood that the cartridge will be automatically fired when it is fully seated within the chamber 68 and the firing pin 12 detonates the primer (not shown) in the base of the cartridge.

To prevent hanging of the rim of the lowermost cartridge behind the rim of the cartridge next above, an inclined ramp or pin 85b straddles the rear of the slot 86 at an angle such that as the lower cartridge is initially directed to the plate 85 from the top right through the opening 67 in the base of the bullet separator, it will be immediately projected forwardly due to the inclination of the pin 85b, as shown in FIGURE 7.

The downwardly inclined surface 850 (FIGURES 1, 6a and 7) along the right leg of the plate further guides the cartridges from the separator into the slot 86. Also, the two ledges 85d, 85d projecting inwardly from both sides of the plate along the rear half thereof, reduce the amount of excess clearance between the cartridge rim and sides of the slot 86 to assist in axially aligning the cartridge with respect to the chamber 68.

Upon the firing of the cartridge, a portion of the force of the recoil is directed through the spent cartridge case 8 against the face of the bolt to drive the bolt rearwardly against the force of the bolt mainspring 18. During the initial retraction period, the top of the bolt supports the next cartridge to be fed into the chamber 68, but when the previously fired cartridge case has driven the bolt rearwardly so that the face of the bolt is no longer under the slot 86, the guide 23 on the oscillating arm 21 will be driven inwardly by action of the bolt cam surface 24 on the rear projection 21a of the arm 21. This inward pivoting of the guide 23 serves to eject the spent cartridge case downwardly to drive it out through the ejection opening in the bottom of the receiver, at which point it will be seen that the mechanism will appear as in FIGURE 7 with another cartridge C resting upon the guide 23 and 7 ready to be driven into the chamber 68 when the bolt is closed. To assist the guide 23 in clearing the receiver chamber of the spent cartridge case, the forward bottom half of the right leg of the plate is provided with a downwardly directed cutout area 85c through which the case is driven by the guide 23 prior to ejection from the weapon.

From the foregoing it will be seen that the arrangement of the oscillating guide arm '21 together with the guide plate 85 and forced feed of the cartridges from the drum magazine enables the weapon to function in any position, even when held upside down.

I claim:

1. A machine gun comprising, a receiver (2), a barrel 1) secured to the forward part of said receiver, a bolt (11) longitudinally reciprocable within said receiver, said bolt including means (12) on the face thereof for detonating cartridges seated in said barrel, spring means (18) constantly urging said bolt forward,

a scar lock (45) pivotally mounted beneath said bolt, said sear lock having an inclined recess (46) in its upper surface and providing a raised locking surface (47) at the rear of said lock, spring means (51) normally urging said locking surface on said sear lock upwards towards said bolt,

stop means (52) on the undersurface of said bolt engageable by the locking surface (47) of said sear lock to retain said bolt in an open cocked position against the action of said bolt spring means (18).

a trigger (32) pivotally mounted adjacent said sear lock, said trigger including sear lock disconnector means (53) at the rear upper edge thereof, said sear lock (45) having an elongated bore (48) extending transversely thereof and encompassing a pivot pin (49) fixedly connected to said receiver, the elongation of said bore extending axially of said machine gun, said sear lock also having a bore extending longitudinally thereof and connecting at its inner end with said elongated transverse bore, and plunger means (50) disposed within said longitudinally extending bore and normally spring urging said sear lock (45) rearwardly away from said disconnector means (53) on said trigger,

whereby, when said bolt is cocked and engaged by said lock the lock will be moved to the forward limit of said elongated transverse bore in said lock to position the forward end of said lock above the rear edge of said disconnector means, and subsequent pivoting of said trigger will release said sear lock from engagement with said bolt.

References Cited UNITED STATES PATENTS 2,174,851 10/1939 Williams 89148 2,548,622 4/1951 Sampson et al. 89-140 X 2,785,605 3/1957 Jourdat 89-140 BENJAMIN A. BORCHELT, Primary Examiner.

S. C. BENTLEY, Assistant Examiner. 

